Mix, Match, And Mutate

Looking for a place to live last year, Paul Rademacher pored over Silicon Valley rentals on craigslist, the popular online classified-ad site. But the 3D-software engineer grew frustrated that he couldn't see the properties' locations on one map. So Rademacher hacked his own solution -- a Web site that combines craigslist rentals with search engine Google Inc.'s (GOOG
) map service. The listings on HousingMaps.com appear as virtual pushpins on maps of nearly three-dozen regions around the country. Click on one, and up pop the details. Since its public debut in April, the free site has drawn well over a half-million unique visitors.

What they're all seeing is nothing less than the future of the World Wide Web. Suddenly, hordes of volunteer programmers are taking it upon themselves to combine and remix the data and services of unrelated, even competing sites. The result: entirely new offerings they call "mash-ups." They're the Web versions of Reese's ("Hey, you got peanut butter on my chocolate!") Peanut Butter Cups.

"The Web was originally designed to be mashed up," says Google Web developer Aaron Boodman, the 27-year-old creator of a program called Greasemonkey that makes it easy to create and use mash-ups. "The technology is finally growing up and making it possible."

That's why mash-ups, named after hip-hop mixes of two or more songs, are starting to rock. Chicagocrime.org overlays local crime stats onto Google Maps so you can see what crimes were committed recently in your neighborhood. Another site syncs Yahoo! Inc.'s (YHOO
) real-time traffic data with Google Maps. Book Burro notices when you're shopping at an online bookstore such as Amazon.com Inc. (AMZN
), then taps into several other stores to show price comparisons.

WILD, WILD WEB

Mash-ups portend big changes for software companies, Web sites, and everyone online. No longer just a collection of pages, the Web is morphing into a sort of global operating system, à la Microsoft Corp.'s (MSFT
) Windows. And now, people are learning to program Web 2.0 with much of the same innovative energy of the personal computer's early days. "It's the Wild West all over again," says Alan Taylor, a Monster Worldwide Inc. Web developer who created Amazon Light, a fast-loading version of Amazon's site that also includes services from Google, Yahoo, and others.

The upshot: People are seizing far more control of what they do online. In the process, those efforts are putting skin on the bones of Web services, the long-delayed promise of software and services that can be tapped on demand. "They're taking little bits and pieces from a number of companies and stitching them together in some clever way," Amazon Chief Executive Jeffrey P. Bezos noted recently. "You'll start to see the real power of Web services."

At the same time, these bottom-up efforts present tough challenges for the sites on which the new services are built. Mash-ups often use the data without asking first, then present it in unintended ways. Not surprisingly, some Web site operators have bitten back. Yahoo initially blocked one mash-up site from using its traffic data with Google Maps before relenting, and Amazon asked Amazon Light's Taylor to change how it linked to potential rival sites. "All this definitely keeps us on our toes," says Jeffrey S. Barr, Amazon's Web services evangelist.

Some mash-up software presents a potential danger to users as well. Greasemonkey, an add-on to the Firefox browser, allows the quick installation of software "scripts" to customize the way a Web site works on a particular PC. Crooks could write malicious scripts -- say, to secretly log keystrokes to steal financial data, says Book Burro creator Jesse Andrews. But he thinks the threat can be minimized with software tweaks and peer review of scripts.

INEXPENSIVE R&D

In any case, none of that has slowed the mash-up momentum. For one thing, Amazon and other Web giants are now embracing the mash-up movement by offering developers easier access to their data and services. Moreover, they're programming their services so that more computing tasks, such as displaying maps onscreen, get done on the users' PCs rather than on their far-flung servers. Besides speeding up the experience, the shift makes it easier for outsiders to add their tweaks, says Google Maps product manager Bret Taylor.

The appeal for Web sites? Mash-ups offer a way for them to tap the creativity and hard work of the masses, who do the work and get out the word -- and the software -- through blogs and Web sites. "We want to encourage community participation," says Paul Levine, general manager of Yahoo! Local. "It's essentially research and development and marketing for us."

The results are often remarkable. Chicagocrime.org, for instance, combines two services -- a Chicago Police Dept. crime Web site and Google Maps -- and lets you type in an address to see recent crimes nearby. The site attracted 1.2 million page views in just the first two weeks after it began in May. Creator Adrian Holovaty, a full-time Web developer at the Lawrence (Kan.) Journal-World's online unit, thinks there may be a business in mash-up creation.

So far, mash-up business models don't extend beyond running a few Google ads and collecting fees for sending buyers to e-commerce sites. One reason is that most Web sites don't allow for-profit use of their data by outsiders. But as traffic to mash-ups grows, companies may cut deals -- especially if mash-up sites spur new markets. Map-based mash-ups, for instance, might finally attract ultra-local businesses to advertise on the Web.

Or Web sites may do their own mash-ups. Amazon's A9.com search site is essentially a mash-up that can be customized by each user, who can query specific sites such as The New York Times or NASA without leaving A9. If A9 can become a mash-up middleman, empowering mere mortals to remix their Web, it could get a leg up on rivals. The idea may have corporate appeal, too: Startup Rearden Commerce Inc. aims to create a Web concierge that lets each user combine the services of many sites.

For now, most mash-ups remain high-tech versions of Tinker Toys. After all, how seriously can you take "Google Map of the Stars," which zooms in on sites such as Neverland Ranch? But from such whimsical experimentation the next tech blockbuster often emerges.